Field of the Invention
The present invention relates to a rotary machine abnormality detection device for detecting abnormality of a rotary machine, a rotary machine abnormality detection method, and a rotary machine provided with the rotary machine abnormality detection device.
Description of the Related Art
A rotary machine such as, for example, an electric motor, a generator, a compressor, and a pump, comprises a rotating body that rotates axially with respect to a prescribed axis. Such a rotary machine is used in various plants and abnormality of the rotary machine is detected to secure a normal operation state. Techniques for detecting such abnormality are disclosed, for example, in JP 5-231361 A and JP 9-133577 A.
A diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A comprises an AE sensor for detecting an AE wave generated by a contact of a male rotor and a female rotor during rotor rotation in a non contact-type oil free screw compressor, an amplifier for amplifying and demodulating the detected AE signal, a device for subjecting the amplifier output to a frequency analysis and an addition averaging processing, a rotor rotation pulse detector for detecting a rotation signal of the rotors and converting the rotation signal into a rotation pulse, and a device for comparing the processing result with a criterion based on the rotation signal, and evaluating and outputting the existence of contact of rotors and the like. More specifically, in the diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A, the existence of contact of rotors is determined by comparing the AE signals of rotational first-order period frequencies of the male rotor and the female rotor, which are generated when the rotors contact each other once per rotation, with a threshold value, or comparing the AE signals of rotational second-order period frequencies, which are generated when the rotors contact each other twice per rotation, with a threshold value.
An abnormal contact detection device disclosed in the above-mentioned JP 9-133577 A detects an abnormal contact state in a rotary machine in which a first rotor and a second rotor rotate as a pair, and comprises an AE sensor for detecting an elastic wave signal emitted from the rotary machine, a demodulation circuit for demodulating the elastic wave signal, a contact determination portion for determining a contact based on a demodulation signal that is demodulated by the demodulation circuit, and an output portion for outputting a result determined by the contact determination portion. More specifically, the contact determination portion determines a contact between the rotors when at least one of a rotational frequency component of the first rotor and a rotational frequency component of the second rotor is included in the demodulation signal at a prescribed level or more. It determines a contact between the rotor and a casing when a frequency component obtained by multiplying the number of blades of the first rotor by a rotational frequency of the rotor and a frequency component obtained by multiplying the number of blades of the second rotor by a rotational frequency of the rotor are included in the demodulation signal at a prescribed level or more. It determines a contact between a sealing material and the rotor when all of the rotational frequency component of the first rotor, the rotational frequency component of the second rotor, the frequency component obtained by multiplying the number of blades of the first rotor by the rotational frequency of the rotor and the frequency component obtained by multiplying the number of blades of the second rotor by the rotational frequency of the rotor are included in the demodulation signal at less than their prescribed levels, and the demodulation signal is more than a prescribed level.
Specifically, in the diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A, the detection is performed in such cases where the rotors contact each other once per rotation, the rotors contact each other twice per rotation, and the like. For example, when the male rotor has 4 blades A1 to A4 and the female rotor has 6 concave portions B1 to B6 which engage with the blades, combinations of the blades A1 to A4 and the concave portions B1 to B6 have 12 patterns, and all combinations are achieved when the male rotor rotates 3 times and the female rotor rotates twice (one cycle of 12 combinations are completed and the initial combination starts over). Thus, when the detection is performed in a case where the rotors contact each other once per rotation, the diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A performs the detection when the blade A1 contacts the concave portion B1, the concave portion B5, and the concave portion B3 while the male rotor rotates 3 times and the female rotor rotates twice. In this example, the diagnostic device performs the detection without being able to discriminate the following cases: a case in which the blade A1 contacts only the concave portion B1 while the male rotor rotates 3 times and the female rotor rotates twice; a case in which the blade A1 contacts only the concave portion B5 while the male rotor rotates 3 times and the female rotor rotates twice; and a case in which the blade A1 contacts only the concave portion B3 while the male rotor rotates 3 times and the female rotor rotates twice. That is, the diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A cannot individually detect contact conditions of 12 different patterns. In reality, however, there is such a case where the blade A1 contacts only the concave portion B1 while the male rotor rotates 3 times and the female rotor rotates twice. Thus, the detection of such an individual contact is needed. Further, the above-mentioned JP 5-231361 A describes an engagement between the male rotor and the female rotor, however, this engagement refers to a case where any given blade of the male rotor contacts any given concave portion of the female rotor. Therefore, the diagnostic device of compressor disclosed in the above-mentioned JP 5-231361 A cannot individually detect the contact conditions of 12 different patterns.
Further, the abnormal contact detection device disclosed in the above-mentioned JP 9-133577 A determines the contact between the rotors themselves, the contact between the rotor and the casing, and the contact between the sealing material and the rotor, but does not detect individual conditions of these contacts.
The present invention is made in view of the above circumstances and the object of the invention is to provide a rotary machine abnormality detection device capable of determining abnormality with higher accuracy, a rotary machine abnormality detection method, and a rotary machine provided with the rotary machine abnormality detection device.